ytdl-org/youtube-dl · error · NotImplementedError

Function String.%s is not yet implemented

Error message

Function String.%s is not yet implemented

What it means

Error "Function String.%s is not yet implemented" thrown in ytdl-org/youtube-dl.

Source

Thrown at youtube_dl/swfinterp.py:548

                    mname = self.multinames[index]
                    arg_count = u30()
                    args = list(reversed(
                        [stack.pop() for _ in range(arg_count)]))
                    obj = stack.pop()

                    if obj == StringClass:
                        if mname == 'String':
                            assert len(args) == 1
                            assert isinstance(args[0], (
                                int, compat_str, _Undefined))
                            if args[0] == undefined:
                                res = 'undefined'
                            else:
                                res = compat_str(args[0])
                            stack.append(res)
                            continue
                        else:
                            raise NotImplementedError(
                                'Function String.%s is not yet implemented'
                                % mname)
                    elif isinstance(obj, _AVMClass_Object):
                        func = self.extract_function(obj.avm_class, mname)
                        res = func(args)
                        stack.append(res)
                        continue
                    elif isinstance(obj, _AVMClass):
                        func = self.extract_function(obj, mname)
                        res = func(args)
                        stack.append(res)
                        continue
                    elif isinstance(obj, _ScopeDict):
                        if mname in obj.avm_class.method_names:
                            func = self.extract_function(obj.avm_class, mname)
                            res = func(args)
                        else:
                            res = obj[mname]

View on GitHub (pinned to 956b8c5855)

Solutions

1. Update youtube-dl; that String method is not implemented in the SWF interpreter.

When it happens

Trigger: Thrown at youtube_dl/swfinterp.py:548 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of ytdl-org/youtube-dl@956b8c5855 (2026-08-14). Data as JSON: /api/errors/78d9ffb79ec12ebd. Report an issue: GitHub.